I usually try to schedule my ride and driving days to work so that I don't have to carry anything with me on the bike. Every now and then I might be caught wanting to ride without having clothes at work, and so then I have to take a small backpack, which I really hate. It feels like it restricts my movement too much, and of course the back sweat issue.

I always use my road bike, because my MTB is just terrible for commuting, even with road tires and a rigid fork. Neither bike has rack provisions. I'm considering a beam rack and trunk bag to use some days, but I've read a few posts here saying that it can sway and make bike handling a bit finnicky. I would also have to swap my current carbon seat post for an aluminum post, which I'm not really crazy about either. I love the comfort that the CF post provides.

Post racks are fine. I use one for my commute on my mountain bike. The main rasks are rack falling apart and/or swinging sidewise due to weight. Neither happened to me yet even I use one with QR lock. Make sure you don't load it up with heavy stuffs. Adding side panniers will be more risky due to added weight and the possibility of hitting the rear wheel when swinging.

As for handling it does make the bike a bit more back heavy and less agile, but nothing serious. I did all my long distance rides / hilly rides / century (only one so far) will my rack.

I have one and find it works well as long as I don't overload it (more than 25 lbs.). Mine is not a quick release and has never slipped. For me the downside is that they tend to hold the load a bit higher, changing the bike's center of gravity. I couldn't imagine even thinking about using one on a carbon post.

I have a Topeak beam rack (with the side rails installed) and a couple of different QR trunk bags that I use when commuting on my FG. As long as I really tighten it down (and don't overload it - I normally only carry lunch and maybe some extra layers), I find it plenty stable. Not sure how well it'd work if I had to carry a laptop, full change of clothes, shoes, etc. On my winter commuter, I installed a regular rack (and fenders) because I can - it's better.

It's not terrible in practice. As far as handling goes, with a seat post rack and light commuting load I couldn't really tell it was there. A little heavier is all. It's just a terrible thing to do to your nice sporty carbon road bike.

I used a Topeak beam rack with a carbon seatpost for about 3 years. It worked well for me. Never swayed and I didn't break the seatpost. I only replaced it because the Topeak bag eventually died (broken zippers and a hole on one side). So, a beam rack and CF seatpost can be done.

It's not terrible in practice. As far as handling goes, with a seat post rack and light commuting load I couldn't really tell it was there. A little heavier is all. It's just a terrible thing to do to your nice sporty carbon road bike.

heh my bike isn't actually carbon. It's a Felt Z85 aluminum bike, but it does have a carbon seat post and carbon forks, which make for a really nice ride.

The load would only be pants and a shirt, undershirt, socks, and undies. Couple of small bottles of shower stuff. Maybe a towel if I don't have one at work. My shoes are really light weight and can be rolled up if needed (Stem Primal Origins minimalist shoes). So the load itself isn't really much at all. I think I could put it in a trunk bag.

I like the Topeak racks that are made for different sizes of bikes and frames. The one for L and XL frames actually angles down from the clamp, to place the load lower to the ground. The one for XS and S frames angles up to help it clear the back tire. I would get the L/XL model for mine, since the top of my seat tube is several inches above my rear tire on a Felt 56 frame.

I did check both Topeak and Bontrager and they both say to not use them with CF seat posts.

My wife and I use the Topeak one on our mountain bikes. It has the quick release but I took that part off and just use the bolt. That way I can tighten it down enough so it does move. Using the quick release and the larger Topeak bag with a load it would move a little. It works great now even on the dirt roads we travel on.

I had one and really did not like it. With any kind of weight at all it would shift to one side or the other. Once when I went over a rough set of railroad tracks it bounced so badly that it knocked my fender out of alignment. Mine also didn't work well with panniers because there was nothing to attach the bottom of the pannier to, which meant that the pannier would swing away from the bike when I turned corners.

You might be able to make it work with a basket or milk crate if you don't carry much weight.

Well that's why I was thinking of just using a trunk bag. Although Topeak does make a beam rack with side extensions to support panniers. I don't think I would ever want to use them on a rack supported only at that single point of the seat post.

I had a Performance brand QR rack, and it eventually broke and dropped on my rear wheel. Swung to the side if not super tight, and carried the load very high, making bike handling less than ideal. Other brands may be better durability-wise, but I really dislike them. Performance gave me a full refund thankfully, and I purchased a Topeak Explorer rack, which is still going strong after many years.

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Quote:

Originally Posted by PatrickGSR94

I usually try to schedule my ride and driving days to work so that I don't have to carry anything with me on the bike. Every now and then I might be caught wanting to ride without having clothes at work, and so then I have to take a small backpack, which I really hate. It feels like it restricts my movement too much, and of course the back sweat issue.

I always use my road bike, because my MTB is just terrible for commuting, even with road tires and a rigid fork. Neither bike has rack provisions. I'm considering a beam rack and trunk bag to use some days, but I've read a few posts here saying that it can sway and make bike handling a bit finnicky. I would also have to swap my current carbon seat post for an aluminum post, which I'm not really crazy about either. I love the comfort that the CF post provides.

You can put a rack on any bike you like with P-clamp. If you want something better than p-clamp, you can go with Tubus stay mounting clamps. They cost more than a p-clamp but they are easier to mount and use. Here's a p-clamp mount

A bit off-topic but might a large frame bag meet your needs? I have the Ibera large size and it is great for fitting to the bike of the day when I need to carry incidental cargo. E.g. when riding to the pub, I carry my lock, flip flops, wallet, phone etc. in it.

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I also used my seatpost rack with a basket where I zip tied the end next to the seat to the seat rails, thereby eliminating the problem of shifting. still allows one to cut it and take it off when you want to "race" the bike.

I have the Topeak QR beam rack and use regular panniers on it to keep the center of gravity lower. Any good quality rack will give you great service and you will never want to use a backpack again once you experience the freedom and getting the weight off yourself and your bum and get it on the bike where is should be. It will make the bike feel a little heavier but you're commuting not racing.

Be careful not to overload a beam rack. I had one for a few months. I would put my thermos of coffee (about 1 liter) on it. It worked great right up until the weight was too much for the rack and it broke. It sheared right through, and was hanging by a tiny bit of metal. I had to ride with my coffee in hand for the next 5 miles.

I had a Koki Halfback rack/trunk on my cannondale. Mfr said it would work with a CF seatpost, and I never had any issues. My wife has one on her Madone 4.7- CF frame and seatpost, and has had no issues in several thousand miles.